Since optical discs such as a CD (Compact Disc) and a CD-ROM (Compact Disc Read Only Memory) are easy to handle and produced at relatively low cost, they have been widely used as recording mediums that store data. In recent years, a CD-R (Compact Disc Recordable) disc and a CD-RW (Compact Disc ReWritable) disc have come out. Data can be easily recorded to these discs. Thus, optical discs in accordance with the CD standard such as a CD-DA disc, a CD-ROM disc, a CD-R disc, and a CD-RW disc are becoming the main stream of data recording mediums. In addition, in recent years, using MP3 (MPEG1 Audio Layer-3) and ATRAC (Adaptive Transform Acoustic Coding) 3, audio data is compressed and recorded on a CD-ROM disc, a CD-R disc, a CD-RW disc, or the like.
However, as a CD-R disc and a CD-RW disc have come out, data recorded on a CD can be easily copied. Thus, a problem about copyright protection has arisen. It is necessary to take countermeasures to protect content data of a CD from being recorded.
FIG. 17 schematically shows a flow of a copy operation. A reproducing apparatus denoted by reference numeral 71 reproduces data from an original disc for example a CD 72. Reference numeral 73 represents an optical pickup. Reference numeral 74 represents a reproduction signal processing portion. Reproduction data is supplied from the reproducing apparatus 71 to a recording processing portion 82 of a recording apparatus 81. An optical pickup 83 records the reproduction data to an optical disc for example a CD-R 84. Recorded contents of the original CD 72 are copied to the CD-R 84. Using the reproducing apparatus 71 and the recording apparatus 81, a copied disc of the original CD 72 can be easily produced.
For a CD, to decrease a DC component of a digital signal that is recorded, EFM (Eight to Fourteenth Modulation) is performed. In the EFM, each data symbol (eight data bits) is converted into a code symbol of 14 channel bits. Three connection bits are added between two sequences of 14 channels bits.
As related art, a method for prohibiting digital information from being copied in accordance with a characteristic of a digital modulating system such as the EFM is described in Japanese Patent Laid-Open Publication No. HEI 9-288864. In the related art, a special encoder and a standard encoder are used. In a standard encoder, DSV (Digital Sum Variation) is cumulated in one direction. In a special encoder, the DSV is prevented from being cumulated in one direction. When a predetermined data sequence is re-encoded by a standard encoder, since the DSV diverges, data cannot be normally reproduced. Using that characteristic, contents can be prevented from being copied.
To determine whether the disc is an original disc or a copied disc, when an original disc is produced, a defect is recorded. When the defect is detected in data reproduced from a disc, it can be determined that the disc is an original disc. In such a method, there is a problem of which original disc contains such a defect. In addition, depending on the type of a defect, it may be able to be copied. As a result, the contents of the original disc cannot be prevented from being copied to a CD-R disc. In addition, unlike a standard encoder that causes the DSV to diverge, a special encoder that prevents the DSV from diverging has a limited number of types of data that can be used. As a result, a complicated data control that also includes an error correction encoding process is required.
Therefore, an object of the present invention is to provide data recording method and apparatus, a data recording medium, and data reproducing method and apparatus.